"H-I" My Gyrocopter By James W. Higgins, EAA 7692 Y es, I have built and flown a gyro- copter, which I consider no great accomplishment as many homebuild- ers have successfully built and flown them long before and since I built mine. From the beginning this project presented a challenge to me, so I undertook to overcome it "from scratch". I'll have to admit that this is not the best way to begin a project, especially on an aircraft of this type on which a lot of valuable information can be obtained and the many sets of complete prints that can be purchased at a nominal cost. Judging from my own experience and from that of others that I have talked with on this subject, the savings will more than offset the purchase price, both financially and in the additional information you'll get from them. My copter is basically the same as a Bensen, but as you can see by the drawings I made many changes in the design of the frame. I used a dif- ferent method for securing it, which I call the "block and bolt" method. This simplifies removing and replac- ing any structural members of the craft, allowing easy disassembly. There is no welding except for one weld on the nose wheel spindle and two in the engine mount braces, which are also bolted to the main structure. There can be many varia- tions in the design and structure of the frame, as well as a choice of material used. Many things can be modified to your own desires pro- vided you use good sound judgment Jim Higgins and his copter in accordance with airworthy prac- tices. However, if you do not have A & E experience or have never worked around aircraft, I strongly recommend that you build strictly according to your set of prints. I'd also like to stress a point, or rather points, which cannot be de- viated from to any great degree with- out running into serious trouble. Of course there is a tolerance to these points which will be called out in your set of prints and if you keep well within these you should have no problems. These critical points are blade track, blade alignment and the most important of all, Center of Gravity of the complete craft. Take it from me, don't experiment or play around with this CG outside of the given tolerances. Nor would it be wise to press your luck outside of the blade track and blade alignment tolerances as either is easy enough to check and correct before you risk your neck. It is possible for alignment and track to change while in flight. One should be aware of how to detect it, and when this occurs, the proper procedure is to set your craft down immediately and take corrective ac- tion while you are able. As I said before, I began from "scratch" except for my few years of knowledge and experience gained as an A & E mechanic. I progressed fine up to a point—and that point was one washed-out, clobbered-in gyrocopter! My big mistake was that I had used the "trial and error" method in finding the CG and for rigging the controls. Let me make this clear—it is not at all safe or sensible to use the "trial and error" method on anything as critical as the CG location in this craft, or any other craft for that matter. I knew it to be critical and felt sure that I had found it correctly, or was within a degree or so of it. I made many test runs and kept my power to a minimum. I'd jockey the craft off as sently as possible so as to get the "feel", which was very good experi- ence in that way but it didn't prove a thing about the CG, as I was under- powered. I learned later that as the power and speed is increased it changes the whole situation. As a matter of fact, in my case it washed out the complete craft and just very nearly washed me out with it. On this particular trial I had about 20 mph ground "H-l" speed and turned into a 25 mph wind. I was literally snatched off the ground and went upward and backwards, and came down upside down. For a few split seconds I sup- pose I had the largest rotary lawn mower in the world, but it was short lived. But the pain, the heartache and in; i red pride, and of course the work of rebuilding the craft remained with me for weeks and even months. Another important lesson I learned was how very, very wise it is to wear a crash helmet at all times while flying. Just to own one is not enough, as my wife reminded me at the time. When I washed out my copter I had left my helmet in the car until I made a "little run" and brought the blades up to proper rpm. But things were going so well that I thought I'd just chance it a little further. In the first place I should not even have thought of making Continued on Page 20 Instrument detail SPORT AVIATION 17